Equine case study – inguinal ultrasound in ‘rigs’
A case detailing the new technique used for equine transabdominal ultrasonography in the inguinal region.
This month I want to draw attention to a potentially useful technique described in the most recent issue of Equine Veterinary Education (Coomer et al., 2016).
Retained testicles are not uncommon in equine practice and castration of these animals can pose something of a surgical challenge. One of the key concerns prior to surgery is ascertaining whether the retained testicle is located inguinally or abdominally. Rectal and percutaneous (transabdominal) ultrasound can be used in an attempt to locate abdominal testes, but can be difficult or dangerous (to animal and handler).
The recent study evaluated a new technique for transabdominal ultrasonography solely in the inguinal region which enabled the operators to categorise patients as either having an ultrasonographically detectable inguinal retained testicle or not. Those that didn’t were assumed to have an abdominally retained testicle.
The technique involved thorough examination of the inguinal region using a curvilinear or linear array transducer with horses under heavy standing sedation and restrained in stocks. A total of 141 retained testes were assessed in the study and there were just 2 false positive results (i.e. 2/51 abdominal testes were recorded as having been scanned inguinally) and 2 false negatives (i.e. 2/85 inguinal testes were not imaged and thus assumed to be abdominal), giving a sensitivity and specificity of 98% and 97% respectively for predicting the presence of an inguinally retained testicle. It should be noted that in cases of bilaterally retained testicles it is necessary to perform hormone assays to prove the presence of testicular tissue before scanning is performed, lest the animal simply be a normal gelding!
This paper validates a simplified scanning procedure that should be useful to most equine practitioners in classifying retained testicles as either inguinal or abdominal and thus making appropriate arrangements for the safe surgical removal of the retained testis/testes. It appears simple, quick, and should be safer for animal and operator than a per rectum approach in many cases.
COOMER, R. P. C., GORVY, D. A., MCKANE, S. A. & WILDERJANS, H. 2016. Inguinal percutaneous ultrasound to locate cryptorchid testes. Equine Veterinary Education, 28, 150-154.